fn main() {
    let mut _s = String::new();
    let data = "initial contents";
    let mut s = data.to_string();

    s.push_str("bar");

    println!("Hello, {}", s);

    let s1 = String::from("Hello ");
    let s2 = String::from("world!");
    let s3 = s1 + &s2; //注意 s1 被移动了，不能继续使用

    println!("s3:{}", s3);

    let len = String::from("Здравствуйте").len();
    println!("len:{}", len);
    for c in "नमस्ते".chars() {
        println!("{}", c);
    }
}
